package org.apache.lucene.index;
/**
 * Copyright 2007 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * For each Field, store position by position information.  It ignores frequency information
 * <p/>
 * This is not thread-safe.
 */
public class PositionBasedTermVectorMapper extends TermVectorMapper {
    private Map<String, Map<Integer, TVPositionInfo>> fieldToTerms;

    private String currentField;
    /**
     * A Map of Integer and TVPositionInfo
     */
    private Map<Integer, TVPositionInfo> currentPositions;
    private boolean storeOffsets;

    /**
     *
     *
     */
    public PositionBasedTermVectorMapper() {
        super(false, false);
    }

    public PositionBasedTermVectorMapper(boolean ignoringOffsets) {
        super(false, ignoringOffsets);
    }

    /**
     * Never ignores positions.  This mapper doesn't make much sense unless there are positions
     * @return false
     */
    @Override
    public boolean isIgnoringPositions() {
        return false;
    }

    /**
     * Callback for the TermVectorReader. 
     * @param term
     * @param frequency
     * @param offsets
     * @param positions
     */
    @Override
    public void map(String term, int frequency, TermVectorOffsetInfo[] offsets, int[] positions) {
        for (int i = 0; i < positions.length; i++) {
            Integer posVal = Integer.valueOf(positions[i]);
            TVPositionInfo pos = currentPositions.get(posVal);
            if (pos == null) {
                pos = new TVPositionInfo(positions[i], storeOffsets);
                currentPositions.put(posVal, pos);
            }
            pos.addTerm(term, offsets != null ? offsets[i] : null);
        }
    }

    /**
     * Callback mechanism used by the TermVectorReader
     * @param field  The field being read
     * @param numTerms The number of terms in the vector
     * @param storeOffsets Whether offsets are available
     * @param storePositions Whether positions are available
     */
    @Override
    public void setExpectations(String field, int numTerms, boolean storeOffsets, boolean storePositions) {
        if (storePositions == false) {
            throw new RuntimeException("You must store positions in order to use this Mapper");
        }
        if (storeOffsets == true) {
            //ignoring offsets
        }
        fieldToTerms = new HashMap<String, Map<Integer, TVPositionInfo>>(numTerms);
        this.storeOffsets = storeOffsets;
        currentField = field;
        currentPositions = new HashMap<Integer, TVPositionInfo>();
        fieldToTerms.put(currentField, currentPositions);
    }

    /**
     * Get the mapping between fields and terms, sorted by the comparator
     *
     * @return A map between field names and a Map.  The sub-Map key is the position as the integer, the value is {@link org.apache.lucene.index.PositionBasedTermVectorMapper.TVPositionInfo}.
     */
    public Map<String, Map<Integer, TVPositionInfo>> getFieldToTerms() {
        return fieldToTerms;
    }

    /**
     * Container for a term at a position
     */
    public static class TVPositionInfo {
        private int position;

        private List<String> terms;

        private List<TermVectorOffsetInfo> offsets;

        public TVPositionInfo(int position, boolean storeOffsets) {
            this.position = position;
            terms = new ArrayList<String>();
            if (storeOffsets) {
                offsets = new ArrayList<TermVectorOffsetInfo>();
            }
        }

        void addTerm(String term, TermVectorOffsetInfo info) {
            terms.add(term);
            if (offsets != null) {
                offsets.add(info);
            }
        }

        /**
         *
         * @return The position of the term
         */
        public int getPosition() {
            return position;
        }

        /**
         * Note, there may be multiple terms at the same position
         * @return A List of Strings
         */
        public List<String> getTerms() {
            return terms;
        }

        /**
         * Parallel list (to {@link #getTerms()}) of TermVectorOffsetInfo objects.  There may be multiple entries since there may be multiple terms at a position
         * @return A List of TermVectorOffsetInfo objects, if offsets are stored.
         */
        public List<TermVectorOffsetInfo> getOffsets() {
            return offsets;
        }
    }

}
